A climatology of seasonal freshwater accumulation as a basis for defining the freshwater budget in Baffin Bay and on the Labrador shelf

The western gateway linking the Arctic to the North Atlantic, encompassing Baffin Bay, the Labrador Shelf, and the West Greenland Shelf (called BBLS hereafter), plays an important role in regulating the freshwater budget of the subpolar North Atlantic. This region channels locally and remotely sourced freshwater towards the Labrador Sea, where it influences deep water formation and ultimately enters the lower limb of the Atlantic Meridional Overturning Circulation (AMOC). Recent changes in the BBLS freshwater budget are impacted by enhanced Greenland ice sheet retreat, reduced seasonal sea ice melting, and increasing Arctic Ocean freshwater content. Separating seasonal freshwater accumulation from persistent interannual anomalies of remote origin remains a major challenge, as overlapping time scales can obscure climatologically relevant variability and hinder our understanding of freshwater influences on coastal dynamics, deep water formation, and AMOC variability. Here, we construct a high-resolution weekly climatology of Freshwater Content Change (FCC) in the BBLS, independent of a subjective salinity reference. FCC, in our formulation, represents the actual freshwater volume gained in the region from April to October through regional seasonal processes. Totaling 3509 km 3 , the summer-integrated FCC is in close agreement with independent estimates of the local freshwater budget. The climatology reveals strong regional contrasts in the seasonal evolution of freshwater accumulation, reflecting the combined influences of sea ice melt, glacier runoff, and remotely advected freshwater signals entering through the Canadian Arctic Archipelago and along the West Greenland pathway. The FCC framework provides a physically interpretable description of seasonal freshwater accumulation in this key Arctic–subpolar gateway and a basis for investigating low-frequency freshwater anomalies and their propagation toward the Labrador Sea and the wider subpolar North Atlantic.